(a) Field of the Invention
The invention relates to formiminotransferase cyclodeaminase (FTCD) antigen which is liver specific to serve as a diagnostic tool for Autoimmune Hepatitis type II.
(b) Description of Prior Art
Autoimmune Hepatitis (AIH) is a disorder of unknown etiology responsible for a progressive destruction of the hepatic parenchyma with a high mortality if left untreated (Johnson P. J. et al., 1993, Meeting Report: International Autoimmune Hepatitis Group, Hepatology, 18:998-1005). One of the characteristics of this disease is the presence of circulating autoantibodies in almost 90% of patients' sera. Clinical and serological differences between patients have lead to the classification of AIH into two types. Type 1 is characterized by the presence of anti-smooth muscle (SMA) and/or anti-nuclear antibodies (ANA) in patients' sera, while sera from Type II patients show anti-liver kidney microsomal antibodies type 1 (LKM1) (Homberg J. C. et al., 1987, Hepatology, 7:1333-1339; Maggiore G. et al., 1993, J. Pediatr. Gastroenterol Nutr., 17:376-381). Recently, a new serological marker, anti-liver cytosol type I antibodies (LC1), was identified in 30% of patients with an AIH type II. In addition, LC1 proved to be the only serological marker in 10% of patients tested (Martini E. et al., 1988, Hepatology, 8:1662-1666). This new organ specific autoantibody is a great contribution to the diagnosis of AIH, especially in patients considered so far as seronegative.
Recently, it was found that the liver cytosol recognized by LC1 had a molecular weight of 62 kDa in human liver and of 58 kDa in rat liver (Abuaf N. et al., 1992, Hepatology, 16:892-898). Furthermore, the authors concluded that LC1 is a more specific marker of autoimmune hepatitis type II than the LKM1 (Abuaf N. et al., 1992, Hepatology, 16:892-898).
It would be highly desirable to be provided with a diagnostic tool specific for Autoimmune Hepatitis type II.